Method and apparatus for removing liquid from permeable material

ABSTRACT

Disclosed herein are a method and apparatus for removing liquid from a permeable material, such as slurries, sludges, porous solids and permeable foams. The method and apparatus involve constraining the material to be deliquified such that the material interfaces with at least one surface which is permeable to the liquid to be removed and then heating the material at one or more locations remote from the permeable surface or surfaces. Such constraining and heating of the material causes the in situ vaporization of the liquid in the vicinity of the remote location or locations. The vaporized liquid expands and forces at least some of the remaining unvaporized liquid through the permeable surface or surfaces. Because only a portion of the liquid contained in the material must be vaporized and such vaporized portion is used to remove at least some of the remaining unvaporized liquid (thereby avoiding the necessity of vaporizing all of the liquid contained in the material), significant reductions in the energy required to substantially deliquify the material may be realized through the use of the method and apparatus disclosed herein.

This is a division of application Ser. No. 173,811, filed on Mar. 3,1988, now U.S. Pat. No. 4,818,415 issued Apr. 4, 1989.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for removingliquid from a permeable material, and, more particularly, to suchmethods and apparatus which are especially adapted to deliquify sludgesand slurries which contain particulate matter suspended in a liquid.

BACKGROUND OF THE INVENTION

Over the years, many different methods have been developed for removingliquids from solids. One common method involves a step by which theliquid is evaporated, leaving dry solids. In practice, such anevaporation step is usually preceded by at least one other dewateringstep designed to remove as much liquid as possible before evaporation.The use of a pre-evaporation step or steps is preferred primarily fortwo reasons. First, the large amount of heat required to vaporize theliquid makes the evaporation step exceedingly expensive. Second, thetime required to boil the liquid can make the evaporation step very timeconsuming. Thus, in order to reduce the cost and/or length of theevaporation step, a multi-step liquid removal process might be employedin which an evaporation step is preceded by any one or all of thefollowing pre-evaporation steps: gravity settling; low-pressurefiltration; and high-pressure filtration. Known techniques foraccomplishing these individual steps are discussed in detail in "TheChemical Engineers Handbook".

When separating solids from water, as in the case of a primary watertreatment system, gravity settling typically results in a slurry orsludge that is 1 to 10 percent solids by weight. The sludge can then besubjected to high-pressure filtration producing a filter cake that isapproximately 30 to 40 percent solids by weight. The maximum percentsolids that can be achieved by pressure filtration is limited by thepoint at which "solids hold-up" occurs (i.e., the point in the processat which the solid particles are compressed together to such an extentthat they behave as a rigid block and will not compact further).However, when such a point in the process is reached, a significantamount of liquid still exists within the intersticies between the solidparticles, the ratio of solids to liquid at this point being referred toas the "equilibrium solids concentration". In order to remove theremaining liquid, the filter cake is typically heated above the boilingtemperature of the liquid and the liquid is evaporated off. The amountof energy required to remove the remaining liquid is still extremelylarge, even when such an evaporation step is preceded by a filtrationstep.

Most commercial filtration equipment, such as vacuum filters, leaffilters, centrifuges, belt filter presses and plate and frame filterpresses, are incapable of producing filter cakes having an "equilibriumsolids concentration", and, therefore, in practice, they usually producewhat at best would be about a 40 percent solids filter cake. Tocompletely dry a pound of such a filter cake, 0.6 pounds of liquid wouldhave to be removed. If the liquid were water, at ideal efficiency almost1000 BTU per pound would be required to evaporate the water, assumingsuch evaporation occurred at atmospheric pressure. Additional energywould also be required to raise the temperature of the solid/liquidmixture from ambient to vaporization temperature. Because theconventional drying processes are not 100 percent efficient, values of1500-2000 BTU per pound of water removed are typical for such processes.

In view of the foregoing discussion, there is a real need for a processwhich is more effective than the known methods for removing liquids fromsolids. Because energy conservation is such an important concernnowadays, there is a further need for a deliquification process which,in addition to being more effective than the known methods, is alsoeconomic.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus forremoving liquid from a permeable material involves constraining thematerial such that it interfaces with at least one surface which ispermeable to the liquid contained in the material. The constrainedmaterial is then heated at one or more locations remote from thepermeable surface or surfaces to a temperature sufficiently high tocause in situ vaporization of the liquid in the vicinity of the remotelocation or locations. As the vaporized liquid expands, it forces atleast some of the remaining unvaporized liquid through the permeablesurface or surfaces. The heating step is repeated until substantiallyall of the liquid has been removed from the material, whereby thematerial is substantially deliquified.

Several different types of heating techniques are suitable for use inconjunction with the present invention. They include: direct resistanceheating produced by passing electric current through the material;dielectric heating produced by exposing the material to electromagneticwave energy; and direct conduction heating. The type of heatingtechnique to be employed is dependent upon the desired efficiency andupon the type of liquid being removed.

In one embodiment, the material to be deliquified is constrained in sucha manner that it interfaces with a pair of surfaces located on oppositesides of the material, at least one of the surfaces being permeable tothe liquid contained in the material. By adapting the surfaces forrelative movement toward and away from each other, they can cooperate tocompress the constrained material before and/or during its heating.Thus, prior to the performance of each and every heating step, at leastsome of the liquid can be expressed from the material through thepermeable surface or surfaces. Such expression of the liquid can befacilitated by creating a vacuum on the side of the permeable surface orsurfaces opposite from the constrained material.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is madeto the following detailed description of various exemplary embodimentsthereof considered in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic illustration of an overall system, includingconditioning apparatus and deliquification apparatus, designed tocondition a liquid slurry and then deliquify it in accordance with thepresent invention;

FIG. 2 is a schematic illustration of the deliquification apparatus usedin the system of FIG. 1, such apparatus being shown in a slurry-fillingphase of the deliquification process;

FIG. 3 is a schematic illustration of the deliquification apparatus ofFIG. 2, the apparatus being shown in a liquid-expressing phase of thedeliquification process;

FIG. 4 is a schematic illustration of the deliquification apparatus ofFIGS. 2 and 3, the apparatus being shown in an in situ vaporizationphase of the deliquification process;

FIG. 5 is a graph showing an idealized profile of the temperatureexisting within the material being deliquified during the performance ofthe in situ vaporization phase of the deliquification process;

FIG. 6 is a schematic illustration of the deliquification apparatus ofFIGS. 2-4, the apparatus being shown in a solids discharge phase of thedeliquification process;

FIG. 7 is a schematic illustration of a modified embodiment of thedeliquification apparatus illustrated in

FIGS. 2-4 and 6, the modified embodiment of FIG. 7 being shown in an insitu vaporization phase of the deliquification process;

FIG. 8 is a cross-sectional view, taken along line VIII--VIII andlooking in the direction of the arrows, of the deliquification apparatusillustrated in FIG. 7;

FIG. 9 is a schematic illustration of another modified embodiment of thedeliquification apparatus illustrated in FIGS. 2-4 and 6, the modifiedembodiment of FIG. 9 being shown in a filter cake delivery phase of thedeliquification process; and

FIG. 10 is a schematic illustration of the deliquification apparatus ofFIG. 9, the apparatus being shown in an in situ vaporization phase ofthe deliquification process.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

While the present invention is especially suited for removing liquidfrom slurries of solid particles, it can also be used to remove liquidfrom any permeable, porous solid, provided that the solid is properlyconstrained. Even deformable solids, such as foams, could be deliquifiedin accordance with the present invention. Because the present inventionhas such special utility for deliquifying slurries, the invention willbe described below with particular reference to a slurry deliquificationsystem.

Referring initially to FIG. 1, a liquid slurry containing approximately1 to 10 percent solids by weight is conveyed by a pump 10 from a source12, such as a holding pond, settling tank, clarifier, etc., through aconduit 14 and into a tank 16 where a bar screen 18 or similar deviceremoves large foreign objects (e.g., sticks, rocks, etc.) and depositsthem in a receptacle 20. Another pump 22 conveys the slurry from thetank 16 to a macerator 24, which is driven by a motor 26. The macerator24 grinds up any large particles that have passed through the bar screen18 to thereby homogenize the slurry. A metering pump 28 delivers achemical flocculate from a storage tank 30 to the slurry at a venturiport 32, which is downstream from the macerator 24. The metering pump 28can be slaved to the pump 22 so that the flocculate will be continuouslyadded to the slurry flowing from the macerator 24.

The flocculate is typically a chemical that causes the solid particlesin the slurry to agglomerate and hence separate from the liquid. Theaddition of the flocculate greatly improves the speed and efficiency offiltration. However, the amount of the flocculate added to the slurry iscritical. A general purpose anionic flocculate, such as that supplied byStockhausen Chemical AG, can be mixed with water to achieve a 0.5 to 0.1percent solution by weight of flocculate. There is an optimum mass ratioof slurry to flocculate solution that needs to be achieved. Typically, a50 to 1 ratio of a 0.25 percent solution is added, but the amount ishighly dependent upon the slurry composition. If too much flocculate isadded, the slurry becomes gelatinous and is more difficult to deliquifythan if no flocculate were added. If too little flocculate is added,filtration efficiency is relatively unaffected. The exact amount offlocculate to be added to a particular slurry is best determined bytrial and error.

Next, the slurry and the flocculate must be adequately mixed to achievethe desired results. Mixing times of at least 30 seconds are normallyrequired. Such mixing can be achieved by first passing theslurry/flocculate stream through a static mixer 34, which includes asealed conduit having internal vanes adapted to induce turbulence in theflowing stream, and then into a dynamic mixing chamber 36, whichincludes mixers 38.

Having been properly conditioned, the slurry is now ready for filtrationin deliquification apparatus 40 including cylinder 42, which isimpermeable to the liquid contained in the slurry and which is made froman electrically non-conductive material. An inlet port 44 for the slurryis located at one end of the cylinder 42, while an outlet port 46 forthe dry solids is located at an opposite end of the cylinder 42. A valve48 controls the flow of the slurry from the mixing chamber 36 to thedeliquification apparatus 40.

Pistons 50, 52 are mounted for reciprocating movement toward and awayfrom each other within the cylinder 42, the pistons 50, 52 being movedby any suitable mechanism such as hydraulic actuators. The pistons 50,52 are hollow with electrically conductive filter faces 54, 56,respectively, each of the filter faces 54, 56 having an air flowpermeability in a range of from 5 to about 15 scfm per square inch at 15psi pressure differential. The pistons 50, 52 are also electricallyconductive so that an electrical flow path exists from the filter faces54, 56 to the exterior of the cylinder 42. The electrical flow path alsoincludes a power supply 58, such as a 110 volt 60 cycle power supply ora source of radio frequency current in a range of from about 8×10² toabout 3×10⁵ cycles per second, and a source 60 of line current atconstant voltage. The pistons 50, 52 are connected to a two-way pump 62by flexible conduits 64, 66, each of which is made out of anelectrically non-conductive material. The two-way pump 62 allows thepressure to be lowered inside the pistons 50, 52 and permits coolinggases to be circulated to the filter faces 54, 56 for reasons which willbe explained hereinafter.

The operation of the deliquification apparatus 40 will now be describedwith reference to FIGS. 2-6. Referring to FIG. 2, after the piston 52 ismoved away from the piston 50 to the position shown, the valve 48 isopened to allow the conditioned slurry to flow from the mixing chamber36 to the cylinder 42 and then fill the void between the pistons 50, 52.By operating the pump 62 to lower the pressure within the pistons 50,52, some of the liquid contained in the slurry entering the cylinder 42is drawn through the filter faces 54, 56 and conveyed to the pump 62through the conduits 64, 66. When the void between the pistons 50, 52 isfilled with a slurry mass 68 (see FIG. 2), the valve 48 is closed andthe pistons 50, 52 are moved toward each other (see FIG. 3) while thepump 62 continues to maintain a low pressure condition inside thepistons 50, 52, resulting in additional liquid being expressed throughthe filter faces 54, 56 and conveyed to the pump 62 through the conduits64, 66.

In a typical slurry of fine particulate matter, such as a primarydrinking water sediment sludge, pressure filtration at 200 psi confiningpressure results in a filter cake 70 (see FIG. 4) of 30% to 40% solidsconcentration by weight. To remove the remaining liquid from the filtercake 70, the pressure is maintained on the filter cake 70 by continuingto urge the pistons 50, 52 toward each other and by continuing tomaintain a low-pressure condition inside the pistons 50, 52. The filtercake 70 is then heated so as to cause the in situ vaporization of theliquid located in a central region 72 of the filter cake 70. As thefilter cake 70 is being heated, the filter faces 54, 56 are preferablymaintained at a temperature lower than the vaporization temperature ofthe liquid, thereby ensuring that the greatest temperature rise andhence vaporization will occur only in the region 72. The graph shown inFIG. 5 depicts an idealized profile of the temperature that existswithin the filter cake 70 along a path extending between the filterfaces 54, 56.

As boiling occurs and as the vapor pressure increases in the region 72,the vapor expands and moves in the form of a front through the filtercake 70 towards the filter faces 54, 56, the vapor front sweepingnon-vaporized liquid from the pores of the filter cake 70 and forcingthe non-vaporized liquid out of the filter cake 70 through the filterfaces 54, 56. Because the filter cake 70 is constrained between thecylinder 42 and the pistons 50, 52 during such in situ vaporization ofthe liquid, the cylinder 42 and the pistons 50, 52 must be capable ofwithstanding the vapor pressure of the liquid so that the volume ofenclosure 74 defined thereby does not substantially increase as thevaporized liquid expands.

The particular method of heating is critical, because the filter cake 70should be heated without heating the deliquification apparatus 40.Direct resistance heating is one acceptable heating method. Inaccordance with such a method, electric current at 110 volts and 60 Hz(cycles per second) is passed through the filter cake 70 by attachingthe power supply 58 to the pistons 50, 52 such that as the voltage isapplied across the filter faces 54, 56 of the pistons 50, 52,respectively, the current flows through the filter cake 70 causingresistance heating to occur. Since the filter faces 54, 56 aremaintained at a temperature below the boiling (i.e., vaporization)temperature of the liquid, vaporization occurs at a location (i.e., inthe region 72) which is equidistance from the filter faces 54, 56.

When direct resistance heating is employed, the current flow selected atthe commencement of the heating step is important to the overall processefficiency. More particularly, the character of the temperature profilethrough the filter cake 70 resulting from a given current flow has beenfound to be determinative of displacement efficiency (i.e., the amountof non-vaporized liquid removed per liquid vaporized). In general, acurrent must be selected for a given filter cake 70 such that an optimumbalance is achieved between the ideal temperature profile as shown inFIG. 5 and the heat loss through the filter faces 54, 56.

The current flow at any set voltage during the subsequent stages of theprocess will be automatically regulated by the resulting conductiveproperties of the pore network within the filter cake 70. That is, asthe conductive liquid is removed from the pore network, conductivity andhence current flow are reduced. Thus, the voltage may be increased asconductivity decreases in order to reduce total processing time. THeprocess may be terminated when a predetermined minimum current flow isachieved or when a uniform temperature profile occurs (i.e., when thetemperature of those portions of the filter cake 70 which interface withthe filter faces 54, 56 is equal to the vaporization temperature of theliquid).

The direct resistance heating method works well for permeablesolid/liquid materials whose liquid component is a polar liquid, such aswater or ammonia. To heat materials containing liquids that arenon-polar, such as alcohols and other hydrocarbons, it is desirable thatthe power supply 58 be a radio frequency current source, instead of a110 volt, 60 Hz source, whereby the filter faces 54, 56 would act assending and receiving antennas. The exact frequency of the RE source,which typically would be in a range of from about 3×10⁵ to about 8×10⁸cycles per second, must be tuned in to the optimum frequency of thatwhich can be absorbed by the liquid.

Once substantially all of the liquid has been removed from the filtercake 70, the pistons 50, 52 are moved to the positions indicated in FIG.6 (i.e., positions which would align the filter cake 70 with the outletport 46 in the cylinder 42 of the deliquification apparatus 40). Theoutlet port 46 can then be opened to permit the discharge of thesubstantially deliquified filter cake 70.

Two alternate embodiments of the deliquification apparatus 40 areillustrated in FIGS. 7 and 8 and in FIGS. 9 and 10, respectively. Thevarious elements illustrated in FIGS. 7 and 8 and in FIGS. 9 and 10which correspond to elements described above with respect to thedeliquification apparatus 40 are designated by corresponding referencenumerals increased by one hundred and two hundred, respectively. Unlessotherwise indicated, the alternate embodiments illustrated in FIGS. 7and 8 and in FIGS. 9 and 10 operate in the same manner as thedeliquification apparatus 40.

With reference to FIGS. 7 and 8, a deliquification apparatus 140includes a cylinder 142, which is permeable to the liquid contained in aslurry being processed in the deliquification apparatus 140 and which ismade from an electrically non-conductive material. Pistons 50, 152,which are made from an electrically non-conductive material, includefilter faces 154, 156, which are impermeable to the liquid contained inthe slurry and which are made from an electrically non-conductivematerial. The cylinder 142 is contained within a housing 176, whichcooperates with the cylinder 142 to form an annular chamber 178.Conduits 164, 166 connect the chamber 178 to a pump 162. An inlet port144, which extends through the chamber 178, is provided with a valve148. An outlet port 146 extends through the chamber 178 and communicateswith the cylinder 142. Microwave horns 180 are spaced at 120 degreeintervals around the perimeter of the cylinder 178 (see FIG. 8).Although three of the horns 180 are shown in FIG. 8, only one wouldsuffice. The horns 180 are positioned such that they are in directalignment with a filter cake 170 constrained between the pistons 150,152 and the cylinder 142.

In the operation of the deliquification apparatus 140, the liquidexpressed by the pistons 150, 152 passes through the cylinder 142,rather than through the filter faces 154, 156. After the completion ofsuch a pressure filtration step, the pressure is maintained on thefilter cake 170 and microwave radiation emitted by the horns 180, whichare connected to a suitable power supply (not shown), is absorbed by thefilter cake 170, resulting in its heating in a central region 172. Thetemperature of the cylinder 142 is, at least initially, below thevaporization temperature of the liquid in order to ensure thatvaporization occurs in the region 172. As the resulting vapor frontsweeps through the filter cake 170, the non-vaporized liquid is sweptfrom the pores of the filter cake 170 and forced out of the filter cake170 through the cylinder 142.

The heating step can be controlled by monitoring the temperature of thefilter cake 170 at its periphery (i.e., at that portion which interfaceswith the cylinder 142). When the temperature being monitored reaches theboiling temperature of the liquid, the microwave energy is switched offand the cylinder 142 is cooled by using the pump 162 and the conduits164, 166 to circulate cooling gas through the chamber 178. The heatingstep can then be repeated, with or without the maintenance of anymechanical or other force on the filter cake 170, to remove any residualliquid from the filter cake 170.

With reference to FIGS. 9 and 10, a deliquification apparatus 240includes a cylinder 242, which is impermeable to the liquid contained ina filter cake 270 being processed in the deliquification apparatus 240.Pistons 250, 252 are mounted for reciprocating movement within thecylinder 242. The piston 250 is solid (i.e., impermeable to the liquidcontained in the filter cake 270) and is adapted to be heated to atemperature which is greater than the vaporization temperature of theliquid contained in the filter cake 270. The piston 252 has a filterface 256 which is permeable to the liquid contained in the filter cake270. A conduit 266 connects the piston 252 to a pump 262. An inlet port244 and an outlet port 246, each of which is large enough to receive thefilter cake 270, are provided in the cylinder 242.

In the operation of the deliquification apparatus 240, the filter face256 is at a temperature below the boiling temperature of the liquid tobe removed. The piston 250 is maintained at a temperature above theboiling temperature of the liquid and is either massive enough to avoida significant temperature drop or is provided with heating means capableof supplying enough energy to vaporize a portion of the liquid withouthaving the piston 250 experience a significant temperature drop. Thebest results have been obtained by having the piston 250 at an elevatedtemperature which is approximately 100° F. above the boiling temperatureof the liquid. The filter cake 270 is then placed in the cylinder 242through the inlet port 244 (see FIG. 9) and not allowed to contact thepiston 250. The piston 252 is moved rapidly to bring the filter cake 270into contact with the piston 250. Sufficient force is exerted by both ofthe pistons 250, 252 so as to constrain the filter cake 270 at apressure greater than the vapor pressure of the liquid containedtherein. A partial vacuum can also be maintained inside the piston 252by the pump 262 to evacuate the liquid expelled from the filter cake270. Vaporization of the liquid which interfaces with the piston 250occurs almost instantaneously. As the resulting vapor front sweepsthrough the filter cake 270, the non-vaporized liquid is swept from thepores of the filter cake 270 and forced out of the filter cake 270through the filter face 256.

The heating step can be controlled by monitoring the temperature of thefilter cake 270 at that portion thereof which interfaces with the filterface 256. When the temperature being monitored reaches the boilingtemperature of the liquid, the pistons 250, 252 can be moved away fromthe filter cake 270 and then cooled by using the pump 262 to draw airthrough the inlet port 244 and into the piston 252 through the filterface 256. Alternatively, only the piston 252, including the filter face256, can be cooled, whereby the piston 250 is maintained at or near theelevated temperature referred to above so as to reduce the additionalenergy required to reheat the piston 250 in preparation for theperformance of another heating step for the purpose of removing anyresidual liquid from the filter cake 270.

The deliquification apparatus 240 is primarily intended to deliquify thefilter cake 270 or a permeable, porous solid which contains a liquid.However, it could also be utilized in connection with thedeliquification of sludges and slurries.

It will be understood that the embodiments described herein are merelyexemplary and that a person skilled in the art may make many variationsand modifications without departing from the spirit and scope of theinvention. All such variations and modifications are intended to beincluded within the scope of the invention as defined in the appendedclaims.

We claim:
 1. Apparatus for removing liquid from a permeable material,comprising means for enabling vaporized liquid, as it expands, to forceat least some of the remaining unvaporized liquid through at least onesurface which is permeable to the liquid contained in the material, saidmeans including constraining means for constraining the material suchthat the material interfaces with said at least one surface, and heatingmeans for repeatedly heating the material at at least one locationremote from said at least one surface to a temperature sufficiently highto cause the in situ vaporization of the liquid in the vicinity of saidat least one location.
 2. Apparatus according to claim 1, wherein saidconstraining means includes an enclosure which is capable ofwithstanding the vapor pressure of the liquid, whereby as the vaporizedliquid expands the internal volume of said enclosure does notsubstantially increase as a result of such expansion, and wherein saidenclosure includes said at least one surface.
 3. Apparatus according toclaim 2, wherein said enclosure includes a first surface located on oneside of the material and a second surface located on an opposite side ofthe material, and wherein said at least one surface includes at leastone of said first and second surfaces.
 4. Apparatus according to claim3, wherein said at least one surface includes said first surface andsaid first surface only, and wherein each location of said at least onelocation is adjacent to said second surface.
 5. Apparatus according toclaim 3, wherein said at least one surface includes both said firstsurface and said second surface, and wherein each location of said atleast one location is substantially equidistance between said first andsecond surfaces.
 6. Apparatus according to claim 3, wherein both saidfirst surface and said second surface are electrically conductive. 7.Apparatus according to claim 6, wherein said heating means includes asource of electric current and means for passing the electric currentthrough the material between said first and second surfaces. 8.Apparatus according to claim 7, wherein the flow of electric current isgenerated by connecting said first and second surfaces to a source ofelectric energy oscillating within a range of from about 6×10¹² to about1×10² cycles per second.
 9. Apparatus according to claim 9, furthercomprising terminating means for terminating the flow of electriccurrent between said first and second surfaces when the material in thevicinity of said at least one surface reaches a temperature which issubstantially equal to the vaporization temperature of the liquid. 10.Apparatus according to claim 9, further comprising cooling means forcooling said at least one surface to a temperature which is less thanthe vaporization temperature of the liquid, whereby said at least onesurface can be cooled after the material has been heated.
 11. Apparatusaccording to claim 10, wherein said cooling means cools said at leastone surface before the material is reheated.
 12. Apparatus according toclaim 10, further comprising compressing means for compressing thematerial before the material is substantially deliquified, whereby atleast some of the liquid can be expressed from the material before thematerial is heated.
 13. Apparatus according to claim 12, wherein saidcompressing means compresses the material as the material is beingheated.
 14. Apparatus according to claim 12, wherein said compressingmeans includes said first and second surfaces and moving means formoving said first and second surfaces toward each other.
 15. Apparatusaccording to claim 14, wherein said moving means moves said first andsecond surfaces away from each other to an extent such that thesubstantially deliquified material can be removed from said enclosure.16. Apparatus according to claim 14, further comprising means forcreating a low pressure region externally of said enclosure in thevicinity of said at least one surface, the pressure existing in said lowpressure region being less than ambient pressure to thereby facilitatethe expression of the liquid from the material.
 17. Apparatus accordingto claim 2, wherein said enclosure is not electrically conductive. 18.Apparatus according to claim 17, wherein said heating means includes asource of electromagnetic radiation of a wavelength within a range offrom about 7×10⁶ to about 3×10⁸ angstroms.
 19. Apparatus according toclaim 18, further comprising terminating means for terminating theelectromagnetic radiation when said at least one surface reaches atemperature which is substantially equal to the vaporization temperatureof the liquid.
 20. Apparatus according to claim 19, further comprisingcooling means for cooling said at least one surface to a temperaturewhich is less than the vaporization temperature of the liquid, wherebysaid at least one surface can be cooled after the material has beenheated.
 21. Apparatus according to claim 20, wherein said cooling meanscools said at least one surface before the material is reheated. 22.Apparatus according to claim 20, further comprising compressing meansfor compressing the material before the material is substantiallydeliquified, whereby at least some of the liquid can be expressed fromthe material before the material is heated.
 23. Apparatus according toclaim 22, wherein the compressing means compresses the material as thematerial is being heated.
 24. Apparatus according to claim 22, whereinsaid enclosure includes a first surface located on one side of thematerial and a second surface located on an opposite side of thematerial, and wherein said compressing means includes said first andsecond surfaces and moving means for moving said first and secondsurfaces toward each other.
 25. Apparatus according to claim 24, whereinsaid moving means moves said first and second surfaces away from eachother to an extent such that the substantially deliquified material canbe removed from said enclosure.
 26. Apparatus according to claim 24,wherein said at least one surface includes neither said first surfacenor said second surface, and wherein said apparatus further comprisesmeans for creating a low pressure region externally of said housing inthe vicinity of said at least one surface, the pressure existing in saidlow pressure region being less than ambient pressure to therebyfacilitate the expression of the liquid from the material.
 27. Apparatusaccording to claim 2, wherein said enclosure includes a first surfacelocated on one side of the material and a second surface located on anopposite side of the material, and wherein said at least one surfaceincludes said first surface but not said second surface.
 28. Apparatusaccording to claim 27, wherein said heating means heats the material bydirect conduction heating through said second surface.
 29. Apparatusaccording to claim 28, further comprising terminating means forterminating the direct conduction heating of the material when thematerial in the vicinity of said at least one surface reaches atemperature which is substantially equal to the vaporization temperatureof the liquid.
 30. Apparatus according to claim 29, wherein saidterminating means terminates the direct conduction heating of thematerial by moving said second surface relative to the material suchthat the material does not interface with said second surface. 31.Apparatus according to claim 29, wherein said terminating meansterminates the direct conduction heating of the material by cooling saidsecond surface.
 32. Apparatus according to claim 29, further comprisingcooling means for cooling said at least one surface to a temperaturewhich is less than the vaporization temperature of the liquid, wherebysaid at least one surface can be cooled after the material has beenheated.
 33. Apparatus according to claim 32, further comprisingcompressing means for compressing the material before the material issubstantially deliquified, whereby at least some of the liquid isexpressed from the material before the material is heated.
 34. Apparatusaccording to claim 33, wherein said compressing means compresses thematerial as the material is being heated.
 35. Apparatus according toclaim 33, wherein said compressing means includes said first and secondsurfaces and moving means for moving said first and second surfacestoward each other.
 36. Apparatus according to claim 35, wherein saidmoving means moves said first and second surfaces away from each otherto an extent such that the substantially deliquified material can beremoved from said enclosure.
 37. Apparatus according to claim 35,further comprising means for creating a low pressure region externallyof said enclosure in the vicinity of said at least one surface, thepressure existing in said low pressure region being less than ambientpressure to thereby facilitate the expression of the liquid from thematerial.
 38. Apparatus according to claim 1, further comprisingcompressing means for compressing the material before the material issubstantially deliquified, whereby at least some of the liquid can beexpressed from the material before the material is heated.
 39. Apparatusaccording to claim 38, wherein said compressing means compresses thematerial before the material is heated and before it is reheated. 40.Apparatus according to claim 38, wherein said compressing meanscompresses the material as the material is being heated.